Arsène Wenger has warned his Arsenal defenders to be ready for a fight when they confront Diego Costa at the Emirates Stadium on Sunday as the Premier League leaders seek to break down a psychological barrier by securing a first league win over Chelsea in more than four years.

Mesut Özil will return from a toe injury and Wenger also hopes Alexis Sánchez can feature at some stage having missed the past seven weeks with a hamstring complaint. Sánchez will be monitored in training to ensure there is no risk of a relapse should he play some part against the champions, with Arsenal steeling themselves for the prospect of facing Costa.

The Spain international’s spats with Laurent Koscielny and Gabriel Paulista when the teams met in September led to the Brazil defender’s dismissal for violent conduct, a sanction that was later overturned on appeal by the Football Association. Although Gabriel ended up serving a one-match ban for improper conduct for the manner in which he left the pitch at Stamford Bridge, the FA retrospectively imposed a three-match suspension on Costa for putting his hands in Koscielny’s face and then catching the Frenchman with a flailing arm in the moments just before the flashpoint with Gabriel.

Costa, who is hopeful of playing despite suffering a bruised shin in the draw with Everton last Saturday, has scored five goals in as many games since Guus Hiddink’s arrival as interim manager.

“We have to focus on our own performance and forget a little bit about Diego Costa,” Wenger said. “But we have to be prepared for a battle because Costa gives you a fight. After that, it’s down to the referee.”

Arsenal will go into the match bolstered by the return of Özil and anticipated availability of Sánchez as their walking wounded start returning to contention. Francis Coquelin took part in training on Thursday after a knee injury, a month earlier than anticipated, while Danny Welbeck, absent since last April, should play some part in the squad’s sessions next week.

“The good news is that Özil certainly will be available and, for Sánchez, the next two days will be decisive though, this time, I think he will make it for selection,” Wenger said. “Coquelin is also back in full training, ahead of schedule, and Welbeck will be in full training next week. So those are positive news.

“Tomas Rosicky I think will play for the under-21s on Friday [against Swansea City]. A few players are coming back. It was important we showed we could cope without these players, and had that collective spirit and unity, but it will ensure we have more variety now. The forwards give you goalscoring [potential] and, as well, I think sometimes in games, when you have 70 minutes gone and you have a strong bench, it gives you a big chance to win the game. That variety of problems you can give to the opponent is very important.”

Wenger suggested Sánchez may start Sunday’s game on the bench. “The doubt is about him having been out for a long time and the risk of a setback,” he said. “To be clear on all the tests is one thing. To be clear after training is another. But the intensity of a big game you can never replicate in training and you can make the risk minimal. I’m cautious with him because we cannot afford a setback, which would mean a very long period out. We don’t want to take this risk. But the signs he’s shown in training this week are positive.”